cmlib/CMLibCompilerFlags.cmake

# based on https://github.com/bluescarni/yacma

include(CheckCXXCompilerFlag)

macro(CHECK_ENABLE_CXX_FLAG flag)
  set(CMAKE_REQUIRED_QUIET TRUE)
  check_cxx_compiler_flag("${flag}" CHECK_CXX_FLAG)
  unset(CMAKE_REQUIRED_QUIET)

  if(CHECK_CXX_FLAG)
    message(STATUS "'${flag}': flag is supported.")
    string(CONCAT _CMLIB_DETECTED_CXX_FLAGS "${_CMLIB_DETECTED_CXX_FLAGS} ${flag}")
  else()
    message(STATUS "'${flag}': flag is NOT supported.")
  endif()
  # NOTE: check_cxx_compiler stores variables in the cache.
  unset(CHECK_CXX_FLAG CACHE)
endmacro()

macro(CHECK_ENABLE_DEBUG_CXX_FLAG flag)
  set(CMAKE_REQUIRED_QUIET TRUE)
  check_cxx_compiler_flag("${flag}" CHECK_CXX_FLAG_DEBUG)
  unset(CMAKE_REQUIRED_QUIET)

  if(CHECK_CXX_FLAG_DEBUG)
    message(STATUS "'${flag}': debug flag is supported.")
    string(CONCAT _CMLIB_DETECTED_CXX_FLAGS_DEBUG "${_CMLIB_DETECTED_CXX_FLAGS_DEBUG} ${flag}")
  else()
    message(STATUS "'${flag}': debug flag is NOT supported.")
  endif()
  # NOTE: check_cxx_compiler stores variables in the cache.
  unset(CHECK_CXX_FLAG_DEBUG CACHE)
endmacro()

function(cmlib_set_cxx_standard version)
  # Выбор стандарта по умолчанию (можно переопределить в проекте)
  set(CMAKE_CXX_STANDARD_REQUIRED YES PARENT_SCOPE)

  if(version EQUAL 11)
    set(CMAKE_CXX_STANDARD 11 PARENT_SCOPE)
    set(CMAKE_CXX_EXTENSIONS YES PARENT_SCOPE)
  endif()

  if(version EQUAL 14)
    set(CMAKE_CXX_STANDARD 14 PARENT_SCOPE)
    set(CMAKE_CXX_EXTENSIONS YES PARENT_SCOPE)
  endif()

  if(version EQUAL 17)
    if(${CMAKE_VERSION} VERSION_LESS "3.10.0")
      check_cxx_compiler_flag(-std=gnu++17 HAVE_FLAG_STD_GNUXX17)
      if(HAVE_FLAG_STD_GNUXX17)
        add_compile_options("-std=gnu++17")
      else()
        check_cxx_compiler_flag(-std=gnu++1z HAVE_FLAG_STD_GNUXX1Z)
        if(HAVE_FLAG_STD_GNUXX1Z)
          add_compile_options("-std=gnu++1z")
        else()
          check_cxx_compiler_flag(-std=c++17 HAVE_FLAG_STD_CXX17)
          if(HAVE_FLAG_STD_CXX17)
            add_compile_options("-std=c++17")
          else()
            check_cxx_compiler_flag(-std=c++1z HAVE_FLAG_STD_CXX1Z)
            if(HAVE_FLAG_STD_CXX1Z)
              add_compile_options("-std=c++1z")
            endif()
          endif()
        endif()
      endif()
    else()
      set(CMAKE_CXX_STANDARD 17 PARENT_SCOPE)
      set(CMAKE_CXX_EXTENSIONS YES PARENT_SCOPE)
    endif()
  endif()
endfunction()

if(NOT CMLIB_CXX_FLAGS_AUTODETECTION_DONE)
  set(_CMLIB_DETECTED_CXX_FLAGS "")
  set(_CMLIB_DETECTED_CXX_FLAGS_DEBUG "")

  # Configuration bits specific for clang.
  if(CMAKE_CXX_COMPILER_IS_CLANG)
    # For now it seems like -Wshadow from clang behaves better than GCC's,
    # just enable it here for the time being.
    check_enable_debug_cxx_flag(-Wshadow)
    # New warnings in clang 8.
    # NOTE: a few issues with macros here, let's disable for now.
    # CHECK_ENABLE_DEBUG_CXX_FLAG(-Wextra-semi-stmt)
    # New warnings in clang 10.
    check_enable_debug_cxx_flag(-Wtautological-overlap-compare)
    check_enable_debug_cxx_flag(-Wtautological-compare)
    check_enable_debug_cxx_flag(-Wtautological-bitwise-compare)
    check_enable_debug_cxx_flag(-Wbitwise-conditional-parentheses)
    check_enable_debug_cxx_flag(-Wrange-loop-analysis)
    check_enable_debug_cxx_flag(-Wmisleading-indentation)
    check_enable_debug_cxx_flag(-Wc99-designator)
    check_enable_debug_cxx_flag(-Wreorder-init-list)
    check_enable_debug_cxx_flag(-Wsizeof-pointer-div)
    check_enable_debug_cxx_flag(-Wsizeof-array-div)
    check_enable_debug_cxx_flag(-Wxor-used-as-pow)
    check_enable_debug_cxx_flag(-Wfinal-dtor-non-final-class)
  endif()

  # Common configuration for GCC, clang and Intel.
  if(CMAKE_CXX_COMPILER_IS_CLANG OR CMAKE_CXX_COMPILER_IS_INTEL OR CMAKE_CXX_COMPILER_IS_GCC)
    check_enable_debug_cxx_flag(-Wall)
    check_enable_debug_cxx_flag(-Wextra)
    check_enable_debug_cxx_flag(-Wnon-virtual-dtor)
    check_enable_debug_cxx_flag(-Wnoexcept)
    check_enable_debug_cxx_flag(-Wlogical-op)
    check_enable_debug_cxx_flag(-Wconversion)
    check_enable_debug_cxx_flag(-Wdeprecated)
    # This limit is supposed to be at least 1024 in C++11, but for some reason
    # clang sets this to 256, and gcc to 900.
    check_enable_cxx_flag(-ftemplate-depth=1024)
    check_enable_debug_cxx_flag(-Wold-style-cast)
    check_enable_debug_cxx_flag(-Wdisabled-optimization)
    # This is useful when the compiler decides the template backtrace is too
    # verbose.
    check_enable_debug_cxx_flag(-ftemplate-backtrace-limit=0)
    check_enable_debug_cxx_flag(-fstack-protector-all)
    # A few suggestion flags.
    check_enable_debug_cxx_flag(-Wsuggest-attribute=pure)
    check_enable_debug_cxx_flag(-Wsuggest-attribute=const)
    check_enable_debug_cxx_flag(-Wsuggest-attribute=noreturn)
    check_enable_debug_cxx_flag(-Wsuggest-attribute=format)
    # From GCC 5.
    check_enable_debug_cxx_flag(-Wodr)
    check_enable_debug_cxx_flag(-Wsuggest-final-types)
    check_enable_debug_cxx_flag(-Wsuggest-final-methods)
    check_enable_debug_cxx_flag(-Wsuggest-override)
    # From GCC 6.
    check_enable_debug_cxx_flag(-Wshift-negative-value)
    check_enable_debug_cxx_flag(-Wshift-overflow=2)
    check_enable_debug_cxx_flag(-Wduplicated-cond)
    check_enable_debug_cxx_flag(-Wnull-dereference)
    # From GCC 7.
    check_enable_debug_cxx_flag(-Wrestrict)
    check_enable_debug_cxx_flag(-Waligned-new)
    check_enable_debug_cxx_flag(-fdiagnostics-parseable-fixits)
    check_enable_debug_cxx_flag(-fdiagnostics-generate-patch)
    # From GCC 8.
    check_enable_debug_cxx_flag(-Wcast-align=strict)
    # This is supposed to produce a nice graphical visualization of mismatching
    # template errors.
    check_enable_cxx_flag(-fdiagnostics-show-template-tree)
    check_enable_debug_cxx_flag(-fdiagnostics-show-option)

    check_enable_debug_cxx_flag(-pedantic)
    check_enable_debug_cxx_flag(-Wcast-align)
    check_enable_debug_cxx_flag(-Wcast-qual)
    check_enable_debug_cxx_flag(-Wctor-dtor-privacy)
    check_enable_debug_cxx_flag(-Wdisabled-optimization)
    check_enable_debug_cxx_flag(-Wformat=2)
    check_enable_debug_cxx_flag(-Winit-self)
    check_enable_debug_cxx_flag(-Wmissing-include-dirs)
    check_enable_debug_cxx_flag(-Woverloaded-virtual)
    check_enable_debug_cxx_flag(-Wredundant-decls)
    check_enable_debug_cxx_flag(-Wsign-promo)
    check_enable_debug_cxx_flag(-Wstrict-overflow=5)
    check_enable_debug_cxx_flag(-Wundef)
    check_enable_debug_cxx_flag(-Wno-unused)
    check_enable_debug_cxx_flag(-Wno-variadic-macros)
    check_enable_debug_cxx_flag(-Wno-parentheses)
    check_enable_debug_cxx_flag(-Wstrict-null-sentinel)
    check_enable_debug_cxx_flag(-Wshadow-all)
  endif()

  if(CMAKE_CXX_COMPILER_IS_GCC)
    check_enable_cxx_flag(-fdiagnostics-color=auto)
    # The -Wmaybe-uninitialized flag is enabled by -Wall,
    # but it is known to emit a lot of possibly spurious warnings.
    # Let's just disable it.
    check_enable_debug_cxx_flag(-Wno-maybe-uninitialized)
    # New in GCC 9.
    check_enable_debug_cxx_flag(-Waddress-of-packed-member)

    if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER "5.999")
      # NOTE: GCC >= 6 seems to be wrongly warning about visibility attributes
      # in some situations:
      # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80947
      # Let's just disable the warning for now.
      check_enable_cxx_flag(-Wno-attributes)
    endif()
  endif()

  # cmake-format: off
  if(LSB_DISTRIBUTOR_ID STREQUAL "AstraLinuxSE" AND
     LSB_CODENAME       STREQUAL "smolensk" AND
     LSB_RELEASE        STREQUAL "1.5")
  # cmake-format: on
    cmlib_set_cxx_standard(11)

    set(_CMAKE_TOOLCHAIN_PREFIX "x86_64-linux-gnu-" CACHE INTERNAL "" FORCE)
    set(_CMAKE_TOOLCHAIN_SUFFIX "-4.7" CACHE INTERNAL "" FORCE)
    set(_CMAKE_TOOLCHAIN_LOCATION "/usr/bin" CACHE INTERNAL "" FORCE)
  else()
    cmlib_set_cxx_standard(17)

    # -Wshadow gives a lot of false positives with GCC 4.7.2 in Astra Linux 1.5
    if(CMAKE_CXX_COMPILER_IS_GCC)
      check_enable_debug_cxx_flag(-Wshadow)
    endif()
  endif()

  if(CMAKE_SYSTEM_PROCESSOR STREQUAL "e2k")
    check_enable_debug_cxx_flag(-Wno-invalid-offsetof)
    list(APPEND CMAKE_LIBRARY_PATH "/usr/lib/e2k-linux-gnu")
  endif()

  # Set the cache variables.
  set(CMLIB_DETECTED_CXX_FLAGS "${_CMLIB_DETECTED_CXX_FLAGS}" CACHE INTERNAL "")
  set(CMLIB_DETECTED_CXX_FLAGS_DEBUG "${_CMLIB_DETECTED_CXX_FLAGS_DEBUG}" CACHE INTERNAL "")
  set(CMLIB_CXX_FLAGS_AUTODETECTION_DONE YES CACHE INTERNAL "")
endif()